Efficient removal of polystyrene nanoplastics from complex water system through multiple driving forces with MOF-based composite

Abstract

As emerging contaminants widely present in aquatic environments, micro/nano plastics (MPs/NPs) pose global environmental and biosafety concerns. The efficient removal of MPs/NPs faces challenges such as poor selectivity and low cyclic stability of traditional adsorbents. This study developed an in-situ synthesis strategy to integrate UIO-66 with melamine foam (MF), successfully constructing UIO-66/MF (UMF) composite that combined high adsorption capacity with excellent structural stability. The results showed that UMF achieved adsorption equilibrium for PS NPs within 300 min, with an adsorption capacity of 65.5 mg/g. Moreover, UMF maintained over 93% and 82% adsorption efficiency in a broad pH range (3-10) and under complex aqueous conditions, respectively. Mechanistic analysis revealed that multiple synergistic interactions were involved in the adsorption process, including hydrophobic interactions, electrostatic interactions, π-π stacking, hydrogen bonding and cation-π interactions. Furthermore, we systematically disclosed the factors which led to the decreased adsorption efficiency in tap water and river water. Notably, UMF exhibited exceptional reusability, retaining higher than 81% removal efficiency after 25 cycles. UMF effectively addresses the challenges of MOFs powders instability and recycling difficulties, achieving a balance between economy, sustainability, and practicality. This composite provides a promising solution for remediating MPs/NPs pollution in aqueous environments.